Supercritical hydrothermal fluids from geothermal deep drilling plants are expected as a potential alternative source for the production of electricity in the future. So e.g. the Iceland Deep Drilling Project (IDDP) is being carried out by an international industry and government consortium in Iceland, in order to investigate the economic feasibility of such an alternative. With drillings up to five kilometers into the earth crust, fluid temperatures in the range of 430-550° C. and a fluid pressure up to 250 bar can be achieved. First tests and analysis indicate that such a well, producing supercritical fluid, could have an order of magnitude higher power output than that from conventional high-temperature geothermal wells with a drilling depth of around two kilometers.
Due to the fact, that such fluids from deep drilling wells have a high silica concentration and acidity of around pH 3, the fluids are unsuited as working fluid for driving a steam turbine. A solution to overcome that problem is the usage of a heat exchanger. With such a heat exchanger, heat can be transferred from such a dirty fluid of a first circuit to a clean fluid of a second circuit. Therefore the heater typically comprising a shell, where an inlet is conducted to a feed pipe of the first circuit for transporting the expected supercritical hydrothermal fluid from the geothermal reservoir into the shell and where an outlet is conducted to a drain pipe for transporting the condensed hydrothermal fluid from the shell to a disposal. In working fluid pipes of the second circuit circulates clean feed water from a condenser of the steam turbine into a heat exchange bundle system within the shell and clean and superheated steam from the heat exchange bundle system back to the steam turbine. The steam turbine itself is connected with a generator for producing the electricity. One problem with acidic hydrothermal fluid from a deep drilling well is that the high silica concentration will lead to a scale formation and high acid concentration in the first condensate of the fluid in the shell of the heater, which forms locally at the outside surface of the heat exchange bundle system. This will reduce the performance of the heater and the overall heat exchange system, which leads to a reduced overall power output.